Dielectrically tuned wavemeter



Sept. 14, '1948.

DIELECTRICALLY TUNED WAVEMETER Filed DeC. 30, 1945 lc. G. soNTHEgMER 2,449,182

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Arme/VFY Patented Sept. 14, 1948 UNITI-:D f srATi-:s rares fr ori-*ICE Carl G. Sontheimer, Haddoniield, N. J., assgnor i to Radio Corporation of America, a corporation of Delaware Application `December 30, 1943, Serial No. 516,298

9 Claims. 1

This invention relates generally to microwave apparatus and more particularly to improved methods of and means for providing variable reactance and attenuation of 'microwaves in a waveguide transmission system.

One of the principal disadvantages of many ltypes of conventional waveguide variable attenuators and tuningdevices is that relatively movable metallic elements provide objectionable contact effects which cause undesired variations in the microwave current distribution in the waveguide conductors. Various types of movable metallic contact devices have been developed to minimize this eiiect by locating all movable mechanical contacts at points of minimummicrowave current distribution. A necessity for such construction can be overcome by eliminating relatively movable metallic elements and substituting therefor relatively movable dielectric elements.

It is well known that microwaves may be attenuated by constricting the Walls of a microl wave waveguide transmission system to a dimension less than 1/2 wavelength along the magnetic axis of wave propagation when the dielectric is provided in the constricted waveguide portion1 by employing therein a combination of fixed and movable relatively high dielectric constant elements, proportioned and having dielectric constants such that free transmission of microwaves occurs only` in such regions as are completely occupiedA by both the fixed and movable dielectric elements.

The ratio of the portion of the constricted waveguide employing only an air dielectric, or

only the iixed dielectric, or only the movable.

dielectric, to that of the constricted waveguide portion entirely occupied by both fixed and movable dielectric elements, determines the effective reactance and attenuation of 'the constricted waveguide portion. The portion ofthe onstrictedy waveguide entirely occupied by high `dielectric constant material therefore will provide a transmission path having extremely` low attennation since the effective cutoff wavelength of this portion of the guide will be above-that of the transmitted microwaveenergy.` The resultant attenuation of the entirely constrictedwaveguide portion may be dependent upon thedegree of penetration of the movable high4 dielectric constant material within the constricted waveguide portion. f H

' Theinstant invention is an" improvement upon `the invention described in the copending application of Eugene O. Keizer, SerjNo. 597,467,` led October `23, 1943, Aupon which UAS. Patent 2,427,098 wasigranted on September` 9, `194:7, entitled Variables attenuators for centimeter waves, and assignedto thesame "assignee `as the instant application. One embodiment of the invention described in said copending application comprises a waveguide having a constrictedportion connected, through a tapered waveguide'portion, to a waveguide of conventional dimensions for the frequency to be transmitted.` `A tapered slug of high dielectric constant solid material may be moved longitudinally along the guide to vary the lengthcf the constrcted'waveguide portlonproviding high microwave attenuation. A second embodiment of the invention described in said copending application comprises a constricted waveguide portion including means for introduc- `ing therein a high dielectric constant liquid.

Various mechanical and hydraulic means are disclosed for actuating the high dielectric constant elements in the two embodiments. A

`.Another invention related to theinstant in- `vention is disclosed in the copending U. vS. application of Ernest0. Linder, Ser. No. 485,356,1iiled May 1, 1943, upon which U. S. Patent 2,423,396 was granted on July 1, 1947, entitled Waveguide attenuatorsand assigned to the same assignee as the instant application. The Linder application discloses various means for inserting energy absorptive dielectric elements within a waveguide 'to provide desired microwave attenuation.-

lhe instant invention inclu-des improved means Vfor obtaining the `desire-d attenuation of `microwaves within a portion` of 'a Wave guide transmission system constricted to less than the cutoii Wavelength, wherein a movable solid high constant dielectric element cooperates with a xed high constant dielectric element within the constricted waveguideA portion, to provide a variablelength path of high `microwave attenuation within the constricted waveguide portion.

A iixed low-loss, high constant dielectric element 35; occupyingthe full cross-sectional area of the constricted waveguide 33 for a portion of its length, and a fractional portionof the constricted waveguide portion for the balance of its length, is inserted within the constricted waveguide portion adjacent the generator waveguide 3|. A movable low-loss, high constant dielectric element 31 is longitudinally adjustable within the constricted waveguide portion 33 to provide a region 1I which also is completely occupied by high constant, low-loss dielectric material. The portions of the constricted waveguide which-are entirely occupied by the high constant dielectric elements `provide regions of low microwave attenuation I, II.`

The end portions of the constricted waveguide portion, `iridicaiied as regions III, IV, provide high microwave attenuation eiectively to prevent leakage of microwave energy from the ends of the constricted waveguide 33. An output waveguide 39,` similarly proportioned tothe input waveguide 3|, is` coupled to the constricted waveguide portion 33 within the region II of low microwave attenuation. The resultant attenuation provided by the constricted waveguide portion 33,`there fore, will be relatively low in the regions I and II and relatively high in thefregion V which is of adjustable length. v i

Since the movable dielectric element 31 may be inserted to any desired position within the constricted waveguide portion 33, it will be apparent that the region Y may be made as short or as long as desired, and that the attenuation dependent thereon may be varied from relatively low to relatively high values, The movable dielectric element 31 may include an indicator 4I operated' in cooperation with a fixed scale 13 to indicate the attenuation inserted in the waveguide transmission system for predetermined positions of the i movable solid dielectric element 31;

" Thus the invention disclosed comprises improved methods of and means for inserting variable reactance in a `waveguide transmission system by means of relatively fixed and movable solid low-loss dielectric elements, thereby providing means for` controlling the attenuation or for measuring the frequency of microwave energy in a waveguide transmission system.

Iclaim as my invention: w i

1, An adjustable microwave reactive `device including a waveguide having va constricted portion providing a region of relatively high attenuation at `theoperating microwave frequency and mode of wave propagation with a low dielectric constant low-loss iiud occupying only a predetermined cross-sectional portion of said constricted portion, a iixed relatively higherl dielectric constant low-loss solid element extending for a predetermined distance along the remaining crosssectional portion of said constricted portion,`

means including a second microwave device coupled to said constricted waveguide portion for introducing microwave energy into said constricted waveguide portion, a movable relatively high ing V:ai-waveguide transmission system having a constricted portion thereof providing a region of relatively high? attenuation at the operating microwave frequency and-mode of wave propagation with a low-loss dielectric constant iluid occupyingl only a predetermined cross-sectional portion of `said lconstricted waveguide portion, a fixed` relatively higher dielectric constant lowloss solid element extending for a predetermined distance along the remaining cross-sectional portionA ofsaid constricted portion, means for introducing microwave energy into said constricted waveguide portion, means for deriving attenuated microwave energy from said constricted waveguide portion, a movable high constant low-loss dielectric solid element proportioned to occupy said predetermined cross-sectional portion of said constricted portion and means for adjusting the longitudinal position of said movable element in said constricted portion intermediate said microwave energy introducing means and said deriving means for adjusting said attenuation of said derived microwave energy. ,Y

, 3; An adjustable microwave attenuator includ- `ing a rectangular waveguide transmission system having a constricted portion thereof providing aregion of relatively high attenuation at the operating `microwave frequency and mode of gtionalportion of said constricted portion and means for adjusting the longitudinal position of rsaid movable element in said constricted portion intermediate said microwave energy introducing means and said deriving means for adjusting said l K attenuation of said derived microwave energy.

cluding' `a waveguide having a constricted portion Vfl; An adjustable Vmicrowave tuning device inproviding a region of relatively high attenuation at the operating microwave frequency and mode relatively `higher dielectric constant low-loss solid element extending for a predetermined distance along the remaining crosssectional portion of said constricted portion, means including a second microwave device coupled to' said constricted waveguide portion for introducing microwave energy into said constricted `waveguide portion, a movable relatively high constantrdielectric low-loss solid element proportioned to 'occupy said cross-sectional `portion of said constricted Awaveguide portion land means` for adjusting the longitudinalpo- ,gitio'n'` of said movable element in said constricted waveguide "portion for effectively tuning said 5. An adjustable microwave tuning device including a, rectangular waveguide having a con- 7. stricted portion providing-a .regionv of.- relatively high at,terniationy at .the .operating rncrow.ave frequency and mode` of -wave propagation with low. ,dielectric t constant low-lossvr flu-ld occupying only a predeterinined` rect-angular rcross-sectional portion having one dimension substantially coincidental with the electrical., axislfdmensionoi said constricted portion,l a xed relativelyhigher dielectric constant low-.loss `solid.element ex,- tending for a, predetermined=. distance along the remaining cross-sectional ,portion1 of zsaid constrcted portion, meansincluding,as econd microwave device coupledtofsaid constricted- .waveguide for introducing microwave energy; into .said constric'ted waveguide portion, a movable lrelatively high constantcdielectric llow-loss solid elementproportioned. to `voccigipy Asaid predetermined cross-sectional portion oi said constricted waveguide portion and means for adjusting the lomgitudinal` position of saidl movable Aelement .in saidV constricted portion for `ellectively tuning said c'onstricted waveguide .portion. p

d. An adjustable microwave-wavemeter device including a. wavcguideV having a constricted portion providing `a region of.. relativel'yhigh attenuation at the. operating microwave ,frequency and mode oiwave propagationwith-alow dielectric constant low-loss iiudv occupying; only a predetermined .cross-sec'tionall portion of said constricted portion, `a fixed relatively. higher dielectric constant low-losssolid element extending L,for a predetermined ,distance along the remaining. `cross-sectional portion` of .said cons'tricted'portion, means including a second microwave device coupled to saidconstricted waveguide portion fcrintroducing microwave energy into said constricted waveguide portionamovable relatively high constant .dielectric low-loss solid element proportioned to occupy saidwpredetermined cross-sectional*portion of said constrcted waveguide portionmeans for adjusting the longitudinal position of said movable .elementin said constricted waveguide portion for eiectively tuning said constricted waveguide portion, and an indicator coupled .to saidsecond device and responsive to said microwave energy for indicating the `rasoi-'lance of said tuned devieeto said operating frequency.

7. y An adjustable. microwave wavemeter device' .including a rectangular waveguide having a constricted-portion providing a regionoi relatively hightattenuation atnthe operating .microwave frequency .and mode o.f wave propagation with a low dielectric constantv low-loss fluidf occupying 4only a predeterminedrectangular cross-sectional .portion having.. one dimension substantially coincidental withthe electrical axis dimensionr of said constricted portion, a xed. relatively higher dielectric constant low-loss sld;element'extend. ing for apredetermined distance along. the remaining cross-sectionall portion@oit-,saidv con.- `s tricted portion, meansincluding@ second micro- .wave `device coupled tosadyconstricted waveguideportion -for introducingmicrowave energy into said constr-icted waveguideportiorra movableirelatively high constant dielectric-low-loss solid elementproportioned to occupy said-predetermined,cross-sectional..portion of said constrictectwaveguide portion, vmeans for. adjusting the longitudin al, positionI of.- said.. movable element in` said constrictedwaveguide portion for effectively tun-ing. said constricted waveguide. portion, and an indicator coupledfto said second device and responsive to` said` microwave. energy for indicatingthe resonance of said tunedy device to saidl operating frequency.

r8. VAn adjustable microwave wavemeter device including a waveguide having a constricted portion provid-ing a `region of relatively high attentuation. at the operating microwave frequencyand mode of wave propagation with alow dielectric-.constant low-pass Afluid occupying only aI predetermined cross-sectional portion of said constrieted portion, a. fixed relatively higher dielectric constant low-loss solid element extending for a predetermined distance along the resnai-ning cross-sectional portion of saidconstricted: portion, means including a second microwave devicev coupled to said constricted wave,- guide. portion for introducing .microwave energy into said constricted waveguide portion, a movable relatively 'high constant dielectricl lowloss solid elementpproportioned to occupy-said predetermined cross-sectional portion of said constricted. waveguide portion, means for` adj-usting the `longitudinal.position of. said movable element in said constricted waveguide portion ioreectively tuning said constricted waveguide portion, and an indicator coupled to said movable dielectric element for indicatingsaid tuning of saidconstricted waveguide portion.`

9. Anadjustalole'microwave waverneter device including arectang'ular waveguide having-acon- .strictedportion providing a region .oirelatively liigh .attenuation-at the operating microwave frequency and mode of wave propagation with a; low dielectric constant low-pass uid occupying only. a predetermined rectangular cross-sectional portion having one, dimension substantially coincidental with. the. electrical laxis dimension .of

said constricted portion, a` iixed. relativelyhigher dielectric constant lowfloss solid. element extending-for-a-.predetermined `distance along there- .maining cross-sectional4 `portion of said con.-

strictedportion, means. including asccondmicrowave.` device coupled. to said constricted waveguide .portion for introducing. microwave. energy.` into for. indicating. the; resonance or, saidtuned device to. said operating .frequency A CARL G.SON.'I`HEIMER.

' REFERENCES; errno The following references are' oi -recordin the;

leof this: patent: l

e UNITED STATES 1:rl'lfli'l Number Namer y vDate 2,197,123 King Apr. 16,1194() 2,376,785 KI'aSlk May 22, 1945 

